Let's UNDERSTAND FARMING!

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3. Mealworm Life Cycle.

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In this chapter, we will explore the fascinating mealworm's life cycle, including the egg, larva, pupa, and beetle stages. With ideal conditions, you’ll get four lifecycles on a natural year but many others if you consider having a progressive setup.

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Egg Stage

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The mealworm life cycle begins with the egg stage. The female mealworm beetle lays eggs on a suitable substrate during this stage. The eggs are small and white and hatch into larvae after a few days.

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Ideal conditions for eggs

During this stage, it is important to maintain the appropriate temperature and humidity levels to ensure successful hatching. The substrate should also be kept clean and free from contaminants to prevent the spread of disease. Once the larvae hatch, they will begin to feed on the substrate and grow in size, entering the larva stage of the mealworm life cycle.

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How long it takes for the beetles to lay eggs?

Once the adult beetle emerges from the pupae (cocoon), it undergoes a maturation process that takes approximately two weeks before it is ready to mate and lay eggs. During this period, the beetle's body undergoes changes that enable it to reproduce and continue the mealworm life cycle. This stage is crucial for the survival and propagation of the species, as the female beetle can lay up to 100-200 eggs at a time and up to 500 eggs over its life span.

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Do I need to add food to my egg trays?

You don’t have to worry about adding wet food to the substrate. The larvae are so small, only a few millimetres long, that they are hard to see from the substrate. A good trick to know if they are ready to wet food is to wait until you see many mini-moulting skins on the surface and an evident movement when manipulated. This means there are big enough to engage on kitchen scraps, peelings, carrots or any other veg you’ll want to add.

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How to identify eggs on my trays?

If you are raising mealworms, watching for the small white eggs, which can be laid on any surface, such as the substrate, container bottom, or egg cartons, is essential. On your beetle's trays, these eggs can be identified by their small size, measuring about 2mm in diameter. You can ensure a healthy and productive mealworm farm by monitoring the egg-laying process.

A straightforward way to check for eggs is to incline the substrate to reveal the bottom. There you could appreciate small white clusters made from substrate and eggs. With time, you’ll understand how saturated the bottom is and the number of eggs laid on the trays.

The eggs are, as well mixed with the substrate, so the pasted eggs at the bottom are only a fraction of the total eggs on the trays.

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How often do I need to replace or rotate my trays?

To know more about the system that suits you better, consult the beetle stage and expand further on Level 2: Scaling up the farm, where you’ll get calculations and methods to ensure you’ll get the best outcome and production from your setup.

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Larva Stage

The larva stage is the longest stage of the mealworm life cycle. During this stage, the mealworm larvae feed on the substrate and grow in size. They shed their skin several times as they grow, a process known as moulting. The larva stage lasts for several weeks, depending on the temperature and humidity of the environment.

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About the hatching process

Mealworms will hatch in ideal conditions ten days (+/-3 days) after being laid. Remember, they may take up to 4-8 weeks to hatch under less-than-optimal conditions, such as low temperatures.

You can expect baby mealworms to become visible to the naked eye after a few weeks. They typically gather around the wet food and are best observed shortly after turning on the lights at night. Because this species is photophobic, they will avoid light sources as much as possible.

Newly hatched mealworms are tiny, measuring around 3mm (0.12 inches) in length. They are white to light orange and have six legs and feelers. As they mature, their colour changes to a darker orange/brown.

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How much moulting does the Tenebrio Molitor have?

Mealworms undergo several moults during their larva stage. The number of moults varies depending on environmental conditions such as temperature and humidity. Typically, mealworms will moult between 12 and 20 times before entering the pupa stage.

Note that the mealworm is white after each moulting and would progressively change to orange/brown in a few days. You don’t need to worry about founding these white larvae. But discard any black or straight larvae you’ll find on your trays to avoid potential diseases, but mainly to prevent odours.

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Why is moulting key for your production?

Like any other insects, Mealworm larvae have an exoskeleton made from chitin. This chitin’s key because it’s a molecule with many benefits and uses.

Chitin is an important molecule found in the exoskeletons of insects, including mealworms and the cell walls of fungi. It is also found in crustaceans' exoskeletons and cephalopods' beaks. Interestingly, recent research has shown that chitin can also be beneficial for plants. When plants are treated with chitin, they can become more resistant to pests and disease. Chitin can stimulate the plant's natural defence mechanisms and promote the growth of beneficial microbes in the soil. This makes chitin a potentially valuable tool for sustainable agriculture.

Moulting made from chitin will fragment and mix with frass (SEE ABOUT) to create one of your best organic fertilisers.

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How long does this process take place?

External conditions are vital in explaining how long this process will take. Insects are cold blood temperature, so external values like temperature, light and humidity regulate their growth. These conditions are the ones we manipulate to improve their life cycle and sometimes to retard some depending on the circumstances of the rearing process.

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In an ideal environment of 25 to 28ºC degrees, mealworms would grow for up to 18 weeks.

From weeks 10 to 12 (approximately three months after hatching), they would get greedy and grow medium to large. And on average, by week 12, they reached their peak large commercial size and would start to become pupae progressively.

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Pupa Stage

After the larva stage, the mealworm enters the pupa stage. During this intermediate stage, the mealworm transforms into a pupa and develops into an adult beetle. The pupa stage lasts for approximately two weeks. The pupa is inactive and does not feed during this stage.

The pupae look like a white wiggly cocoon. But, very different from others insects pupae stage produces a hard shell. It can move and rotate the ‘tail’ section when disturbed.

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Pupa evolution in time

Initially, it’s very white and soft and contains humidity, but it gets harder and progressively darker. As soon they get closest to emerging, eyes forming can be observed as dark spots. In the last few days, it can be manipulated, but be very careful in the early soft stage (days one and two) because they can get hurt by any compression on their bodies.

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How to store it?

There’s no need for substrate or feed at this stage. In the insect-rearing industry, there are different techniques to separate and store the pupae that we will explain in other chapters to avoid. The more primitive system is to pick it with your hands or any soft instrument, for example, a plastic spoon to avoid damaging their bodies.

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Troubleshooting

Pupa is the most vulnerable life stage and has high death rates if not appropriately managed. Typical death rates on the lower end are around 10% and up to 25% at the higher end.

The success of normal and healthy beetles emerging from the pupae stage critically depends on the last week or two from the larvae stage. Having great food and good values of humidity and temperature reduce deformations. The deformed pupa has to be discarded as it usually got problems reproducing and laying eggs and would only consume resources on the farm.

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Beetle Stage

The final stage of the mealworm life cycle is the beetle stage. Adult mealworm beetles are black or dark brown and measure between 1 and 1.5 centimetres in length. They are capable of laying eggs and starting the life cycle over again. The beetle stage lasts several weeks; adult beetles can live for up to a year. Beetles are voracious, not so much as in the larvae stage, but they would prefer wet food and their mobility increase, so it’s a good thing to bring some elements on the tray that act as a climbing structure to meet and mate as they prefer to get under the substrate to lay eggs mostly. This species is also photophobic at this stage, so they would avoid light sources and enjoy dark places. If the light is always on, they hide under objects and the substrate.

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Intro

After emerging from the pupa stage, mealworms transform into adult darkling beetles. The beetles have a distinctive morphology that differs from the larvae and pupae stages.

Adult darkling beetles’ size is defined by their pupa size; they can vary from 1 to 1.5 - Exceptionally, some individuals could reach up to two centimetres in length. They have a hard exoskeleton that protects their body. They have a flattened body shape and can range in colour from black to brown.

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Wings

One of the most significant morphologic changes that occur during the beetle stage is the development of wings. Adult mealworm beetles have wings hidden under their hard exoskeleton and are not used for flight. But they are capable of flight, and this usually happens when the Tenebrio Molitor beetles are stressed due to a high density of individuals and the food is scarce. This mobilises it to flight, more like jumping, because they got little control over direction and duration out of the tray. After all, it’s their instinct to expand in search of other food sources.

However, the wings play an essential role in mate selection and communication, as males use their wings to create a distinctive sound that attracts females.

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Reproduction

Another morphologic change that occurs during the beetle stage is the development of genitalia. Mealworm beetles have distinct reproductive organs, and males have a characteristic hook-like structure on the last segment of their abdomen used for mating.

Finally, the digestive system of the adult darkling beetle is also different from that of the larvae and pupae stages. Adult beetles have a complete digestive system with a mouth, crop, proventriculus, gizzard, midgut, and hindgut. The digestive system of the beetle is necessary for breaking down and processing food, and the beetle's diet can affect its reproductive success and overall health.

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Understanding the adult stage

Understanding the morphologic changes that occur during the beetle stage is important for mealworm farmers because it helps them identify and care for their adult beetles. By providing optimal living conditions and a balanced diet, mealworm farmers can ensure that their beetles thrive and produce healthy offspring.

It’s interesting to note that immediately after emerging from pupa, they will appear white and progressively, their chitin exoskeleton will turn to the final brown/dark colour as well as this shell hardener. So, any manipulation of their soft/white stage can damage their body.

Beetles can eat small mealworms, mainly attracted to their water source, so it’s advised to remove them from the container as soon as they appear and place them into a second container where they can lay their eggs on the mealworm substrate.

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Life Expectancy

Approximately 10-14 days after they emerge from the pupa, they mate and lay eggs into the substrate. Remember that the eggs are mixed in with the poo (frass) at the bottom of the container, and this will provide you with the next generation, so don’t throw it all out.

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Beetles have an average life expectancy of approximately 3-6 months, depending on temperature. The most productive breeding occurs in the first 4-6 weeks.  All life stages have a bell shape curve, with some dying earlier, the most dying in the middle, and some taking longer.

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Feeding Beetles

– The adult feeds on cereal, meal and wet  foods.

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^{Documentation Last revision: 07 March 2023 By 01Entolab}

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4. Setting Up a Mealworm Farm.

Continue to next chapter

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^{Documentation Last revision: 07 March 2023 By 01Entolab}

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